Sewage purification



Jmm, 1933. K, IMHOFF 1,893,623

SEWAGE PURIFICATION Filed Aug. 30. 195o 3mm/Worf Patented Jan. 10, 1933 i UNITED STATES PATENT OFFICE KARL IMHOFF, 0F ESSEN, GERMANY SEWAGE PURIFICATION Application tiled August 30, 1930, Serial No. 479,046, and in Germany January 20, 1930.

The present invention relates to sewage more vent openings 13, as shown in the drawpurilication, and more particularly to an aping. paratus and process for the biological puri, The bottom of the settling tank 10. confication of the orga-nically soiled sewage by verges toward a central transverse line, and 5 submerged contact aerators and activated the bottom is slotted and provided with a de- 55 sludge tanks. ficctor 14 extending transversely in the tank Another object of the present invention is l2 and beneath the slot in the bottom of the to provide an apparatus which is relatively settling tank l() for directing the sewage to compact or condensed, which carries out the the opposite sides of the tank l2. This delo process in stages arranged in series and with lector 14 may be in the form of a bar tri- 60 certain improved means for returning cerangular in cross section with an apex projecttain settlings from the different stages for ing up through the slot in the bottom of the reactivating the same and insuring the comtank but in spaced relation to the marginal plete purification and treatment of the sewage edges of the top of 'the tank l0. A 5 throughout the process and the utilization of A second conduit 15 leads out of the upper 65 the excess activated sludge in the different portion of the preliminary settling tank l0 stages in the apparatus. at its side preferably opposite to the sewage A further object of the invention is to prosupply conduit 1l and the conduit l5 is carvide a two-stage activated sludge plant which ried around the adjacent side of the tank l2 requires a space approximately rom thirty as shown in Figure 2 and opens through the 70 to fifty per cent smaller than the heretofore adjacent end wall of a contact aerator tank known one stage plants endeavoring to ob- 16, near the top thereof. tain the same result. The aerator tank 16 is provided with a A still further object of the invention is to stirrer 17 of preferably U-shape and which combine in a process and plant of this charis hollow to receive air adapted to be deliv- 75 acter two-stages with the first stage of the ered in jets through openings 18 formed in submerged contact aerator type and the secthe upper side of the lower cross bar of the ond stage of the activated sludge tank type. stirrer 17. The stirrer 17 is of suitable Width lrVith the foregoing and other objects in and length to extend downwardly about the view, the invention will be more fully deinner compartment 19 of the aerator tank 16 80 scribed hereinafter, and will be more particuand is supported upon a hollow cross shaft larly pointed out in the claims appended 20 mounted in suitable bearings 2l across the hereto. top 'of the aerator tank 16.

In the drawing, wherein like symbols refer rom the tank 16 the aerated sewage passes 35 to like or corresponding parts throughout the into a settling tank 22 disposed closely adseveral views. jacent to the aerator tank 16 and connected Figure 1 is a longitudinal section taken thereto by a conduit 23. The conduit 23 through a plant constructed according to the opensinto the upper end of a delivery bell present invention and which may be used in 24 which has its open lower end spaced above carrying out the process of this invention, the bottom of the settling tank 22, and the and .l latter is provided at its upper end with an Figure 2 is a top plan view of the same. inwardly offset overflow wall or dam 25 eX- Referring now to the drawing, 10 desigtending entirely around the upper end of the nates a preliminary settling tank into one settling tank 22 and providing a channel or side and in the top of which opens a conduit passage 26 into which the lighter liquid con- 95 1l for the sewa e. This settling tank 1() is tent of the sewage is adapted to spill. located within t e upper end of a sludge di- The channel 26 opens through a passage 27 gestion tank l2 of suitable depth and conformed in the end wall of the tank 22 remote struction and which is closed at its top by the from the conduit 23. The settling tank 22 settling tank with the exception of one or completes the first stage of the process and tling is supported u the liquor which is separated off from the settank 22 is carried through the opening 27 into the next stage of the plant. l

rI`he second stage of the process calls for the passage of the separated liquor from the first stage into an activated sludge tank 28, and such tank is shown in the drawing as having an end wall in common with the settling tank 22 and through which the opening 27 extends. The separated liquor therefore flows through the opening 27 into the tank 28 and is aerated and agitated in the tank 28 by a pair of hollow depending agitators 29 having perforations in the upper sides of their lower cross bars as shown to advantage in Figure 2 at 30 and which are similar to the stirrers or agitators 17, and each of which on a hollow cross shaft 31 mounted in suitable bearings 32 across the upper edge of the activated sludge tank 28.

From the sludge tank 28 the aerated liquor passes through a conduit 33 in the opposite end Wall of the tank 28 into a second delivery bell 34 which opens downwardly into a second settling tank 35 constructed simii larly to the tank 22 and from the upper portion of which the final liquor is carried off through a conduit 36.

The second settling tank 35 is provided with an air operated injector 37 arranged above the tank 35 and having a fpipe 38 which extends down to the bottom o the tank 35, the latter having a downwardly converging bottom for the purpose of lifting the settled activated sludge out of the tank 35 and delivering the same to a return pipe 39 which extends lengthwise of the tanks and has a first delivery spout 40 opening into the upper end of the activated sludge tank 28 for the return of the larger portion of the settled activated sludge from the second settling tank 35. The return pipe 39 continues rearwardly of the tanks and has its second spout 41 opening into the top of the contact aerator tank 16 so as to return the remainder of the settled sludge from the settling tank 35 in the second stage to the aerator tank 16 of the first stage. Y

The first settling tank 22 is also provided with an air operated injector 42 adapted to lift the settled sludge out of the tank 32 into a return pipe 43 which has a nozzle 44 opening into the conduit 11 for returning such sludge as settles in the tank 32 back into the preliminary tank 10.

The reservoir 45 or other suitable source of air supply is connected by a supply pipe 46 to the hollow shafts 20 and -31 and also to branch pipes 47 which lead to the injectors 37 and 42 for supplying air to these various elements, the connections to the shafts 2O and 31 being rotating or swiveled connections.

The shafts 20 and 31 are each provided with a crank 48 and the cranks are connected to a rod 49 which in turn is connected to a xmotor 50 or the like for the purpose of reciprocating the rod 49 and the shafts 20 and 31 connected thereto. The return pipe 43 may be connected by a branch pipe 51 to the return pipe 39 so that the activated settled sludge raised by the injector 42 may in part be delivered into the forward end of the return pipe 39 and thus into the aerator tank 16 for passage a second time therethrough.

Activated sludge tanks have inside. The carrier of the purifying agent is the activated sludge which forms itself out of the sewage in the tank. This sludge is kept in suspension by stirring the tank contents and is also aerated. On account of this purifying work the activated sludge increases steadily and a certain part thereof must therefore be daily removed as excess activated sludge.

The activated sludge process is superior to the submerged contact aerators in so far as the most complete purifying can be obtained. The process is especially economical when it is arranged in two stages whereby the excess activated sludge of the second stage is not discharged but is returned tothe tanks of the first stage w rectly and attend to the main purifying.

Complete use of the excess activated sludge of the second stage is made in the first stage and the then resulting, completely used excess activated sludge will-be discharged.

Submerged contact aerators having the advantage that they are less sensitive to occasionally appearing industrial poisons and to quick changes in the condition of the sewage, than tanks operated with activated sludge. Submerged contact aerators are in the case of a disturbance, active again in a few hours because the interior structure is stationary. The activated sludge once disturbed must be removed most of the time and it requires one week until the sludge is reconditioned.

In order to combine the advantages of both processes it is suggested that submerged contact aerators be used as first stage and activated sludge tanks as second stage. plant should be so operated that the excess of the activated sludge tank will first be brought into the submerged contact aerator and used for purifying the sewage before it is discharged definitely. In such a manner one combines the advantages of the submerged contact aerators with the ones of the j two stage activated sludge tanks, and receives a purifying process that exceeds economically any process heretofore known.

In operation, the sewage is delivered through the conduit 11 into the preliminary settling tank 10 from which it is discharged and spread into the sludge digestion tank 12. The separated liquor from the top of the preliminary settling tank 11 is carried through the conduit 15 and discharged into no structures.

The

27 into the activated sludge tank i small space,

' 50 two stages, the

the contact aerator tank 16. The agitatoror ing the sludge accumulating in the settling stirrer 17 operates to not only stir up the settlings in the chamber 16 but to also distribute air in tine jets through lhe lighter liquor is then separated from the upper end of the tank 16 and carried into the tir-st settling tank 22. The sludge accumulating in the bottom ot the tank 22 is raised through the pipe 38 by the injector 42 and returned in part to the pipe 39 and .in part to the pipe 43 so that the accumulating sludge is in part returned to the conduit ll for repassage as .an activated material through the preliminary settling and the digestion tanks l0 and 12. The other part of the raised sludge goes back directly into the aerator tank 16 and assists at this point in the apparatus in the destruction of the less activated material in the sewage.

The liquor which settles olf in the top of the tank 22 is carried through the opening 28, is aerated through the jets 30 and is agitated by the stirrers 29..

The separated liquor then passes from the top of the tank 28 into a second settling tank where it is divided by settling and the lighter liquor passes oil through the conduit 36 while the activated sludge in the bottom of the tank 35 is carried back through the pipe 39 as above brought out.

.The structure is such that it occupies but carries ont the' process with rapidity, and combines two separate features in the two dilerentlstages of the operation and of the plant so as to more effec# tively and quickly carry out the desired result.

It is obvious that various changes and modifications may be made in the details of construction and desi of the above specically described embodlment of this invention without departing from the spirit thereof, such changes and modifications being restricted only by the scope of'the following claims:

What is claimed is 1. A sewage treatment rst stage Including a digestion tank, an aerator and a settling tank and the second stage including a sludge tank and mg into the sludge a settling tank, agitators mounted in the aerator and sludge tanks, means for operat-,` ing the agitators, a source of air supply under pressure connected to said agitators for supplying air to the liquor passing through said tanks, return pipes leading from the settling tanks of both stages with the return pipe from the settling tank ing )into the aerator and digestion-tanks and the 'return pipe from the second stage openand aerator tanks, and air actuated means connected to said source of air supply and to said pipes for liftthe liquor.

plant comprising of the first stage open tanks into said return pipes.,

2. A sewage treatment plant connected with a digesting sludge tank' comprising two sta es, the rst stage including an aerator, an a settling tank, and the second stage including sludge tanks-and a settling tank, agitators mounted in the aerator and sludge tanks, means for operating the agitators, a source of air supply lunder pressure in conv nection with the agitators for supplying air to the sewage liquor passin through said aerator and sludge tanks, con nits connecting the tanks of the successive stages for the pas-l sage lof elliuent therethrough, delivery bells in the settling tanks in communication with the connecting conduits leading from the aerator and sludge tanks respetcively, for diffusion of sludge carried over with any emuent,a return pipe leadin from the settling tank ot the first stage'to le aerator, another return pipe from thesettling tank of the first stage opening into the digesting sludge tank and in cross communication with the return conduit leading into the aerator tank, and actuated means connected with said source of air supply and to said return pipes for lifting the sludge accumulating in the settling tanks into said return pipes. 1

In testimony that I claim the foregoing as my inventlon,I I have signed my name hereto.

'KARL OFF.` 

